The invention relates to a coupling for connecting a first pipe part and a second pipe part, comprising a first coupling part which is to be connected to the first pipe part and a second coupling part which is to be connected to the second pipe part, which two coupling parts each have a through passage and can be coupled together in order to bring about a releasable connection between pipe parts which are connected thereto, the through passages in the coupling parts adjoining one another coaxially, and further comprising:
shut-off means, which are arranged in at least one of the two coupling parts, for opening and shutting off the through passage in the coupling part in question, PA0 locking means comprising a first locking member, which is arranged in the first coupling part, and a second locking member, which is arranged in the second coupling part, which locking members are able to interact with one another in order to lock the two coupled-together coupling parts in the axial direction with respect to one another, and are able to move with respect to one another between an unlocked position, in which the two coupling parts can be separated from one another, and a locked position, in which the two coupling parts are coupled together and are fully locked together in the axial direction, via an intermediate position, in which the two coupling parts are coupled together and the locking between them is just active, PA0 actuating means, which are arranged in at least one of the two coupling parts, for actuating the shut-off means, the locking means and the actuating means being designed in such a manner that the through passage in that coupling part in which the shut-off means are arranged can only be opened by means of the actuating means and the shut-off means when the locking means are in the intermediate position or the locked position or between these positions, and the locking means can only be moved out of the intermediate position into the unlocked position when the actuating means and the shut-off means are in the position in which the through passage in the relevant coupling part is shut off.
A coupling of this nature is known from EP-A-0,719,973. In this known coupling, the shut-off means are actuated by the locking means via the actuating means. In the coupled position of the two coupling parts, the locking means are in engagement with the actuating means, which actuating means are entirely enclosed in the coupling part in which the shut-off means are arranged.
The known coupling has the drawbacks that actuation of the shut-off means is directly coupled to the actuation of the locking means and that it is not possible to see directly from outside the extent to which the through passage in the coupling is open or closed. This fact represents a drawback particularly during unlocking and uncoupling.